Glycogen is the principal storage form of glucose in animal and human cells. It is made primarily by the liver and muscles, but it can also be made by glycogenesis within the brain and stomach. Cayman’s Glycogen Assay provides a simple, reproducible, and sensitive tool for assaying glycogen from tissue. In this assay, glycogen is hydrolyzed by amyloglucosidase to form β-D-glucose, which is then specifically oxidized to D-glucono-δ-lactone by glucose oxidase forming hydrogen peroxide in the process. Hydrogen peroxide, in the presence of horseradish peroxidase, reacts with 10-acetyl-3,7-dihydroxyphenoxazine (ADHP) in a 1:1 stoichiometry to generate the highly fluorescent product resorufin which is measure at an excitation wavelength of 530-540 nm and an emission wavelength of 585-595 nm.